I encountered an issue where the data I passed to a component ended up being undefined

Question

I encountered an issue where the data I passed to a component ended up being undefined

So here's the scenario: I'm working on a Next.js project where I have a context for modals. In this context, I store modal details in an array called modalBase. Additionally, I fetch data from another context (toolsContext) to pass it to components. The issue arises when I console log the data in this context - it shows up correctly. However, after passing the data to components, it becomes undefined. I'm quite puzzled by this.

  const [data, setData] = useState();
  const [modals, setModals] = useState([]);

  const router = useRouter();
  const query = router.query;

  const { collectionData } = useContext(toolsContext);

  useEffect(() => {
    const getData = async () => {
      const ss = await collectionData(query.taskId);
      setData(ss);
    };
    getData();
  }, []);

  // ======= Modal details
  const modalsBase = [
    {
      name: "collectCreator",
      openStatus: false,
      content: <CollectionForm />,
    },
    {
      name: "taskItemCreator",
      openStatus: false,
      content: <TaskItemForm data={data} />,
    },
    {
      name: "taskCreator",
      openStatus: false,
      content: <TasksForm data={data} />,
    },
    {
      name: "collectionEdit",
      openStatus: false,
      content: <CollectionEditForm data={data} />,
    },
    {
      name: "taskItemEdit",
      openStatus: false,
      content: <TaskItemEditForm />,
    },
    {
      name: "tasksEdit",
      openStatus: false,
      content: <TasksEditForm />,
    },
  ];

My hunch is that the issue stems from trying to pass data to components within the array.

javascript next.js axios

Answer 1

Answer №1

Your components are encountering an issue with the undefined `data` because it is being initialized asynchronously within a `useEffect` hook, and then immediately utilized in your `modalsBase` array. It's important to note that `useEffect` is executed after the component render, and data fetching is also asynchronous.

As a result, when your `modalsBase` array is defined, the `data` is still undefined. It only receives a value once the data fetching process concludes, at which point the `modalsBase` array has already been defined with undefined data.

To resolve this issue, consider relocating your `modalsBase` array inside a `useEffect` hook that lists `data` as a dependency. This way, the array will be redefined each time `data` changes. Here's an example of how you can implement this:

const [modals, setModals] = useState([]);

 useEffect(() => {
   const modalsBase = [
     {
       name: "collectCreator",
       openStatus: false,
       content: <CollectionForm />,
     },
     {
       name: "taskItemCreator",
       openStatus: false,
       content: <TaskItemForm data={data} />,
     },
     // ...
   ];

   setModals(modalsBase);
 }, [data]);

By doing so, the `modalsBase` array will adapt whenever `data` changes, including during the initial fetch. Consequently, the components will correctly receive the updated `data`.

Additionally, I suggest initializing `data` as null instead of undefined to clearly indicate that it is intentionally empty initially. This allows for conditional rendering based on whether `data` is null or populated. To achieve this, modify the line `const [data, setData] = useState();` to `const [data, setData] = useState(null);`.

Note that constant re-renders may occur whenever `data` updates. If `data` undergoes frequent changes, exploring alternative strategies like incorporating a loading state into components or conducting data fetching directly within said components could be beneficial.

Answer 2

Your components are encountering an issue with the undefined `data` because it is being initialized asynchronously within a `useEffect` hook, and then immediately utilized in your `modalsBase` array. It's important to note that `useEffect` is executed after the component render, and data fetching is also asynchronous.

As a result, when your `modalsBase` array is defined, the `data` is still undefined. It only receives a value once the data fetching process concludes, at which point the `modalsBase` array has already been defined with undefined data.

To resolve this issue, consider relocating your `modalsBase` array inside a `useEffect` hook that lists `data` as a dependency. This way, the array will be redefined each time `data` changes. Here's an example of how you can implement this:

const [modals, setModals] = useState([]);

 useEffect(() => {
   const modalsBase = [
     {
       name: "collectCreator",
       openStatus: false,
       content: <CollectionForm />,
     },
     {
       name: "taskItemCreator",
       openStatus: false,
       content: <TaskItemForm data={data} />,
     },
     // ...
   ];

   setModals(modalsBase);
 }, [data]);

By doing so, the `modalsBase` array will adapt whenever `data` changes, including during the initial fetch. Consequently, the components will correctly receive the updated `data`.

Additionally, I suggest initializing `data` as null instead of undefined to clearly indicate that it is intentionally empty initially. This allows for conditional rendering based on whether `data` is null or populated. To achieve this, modify the line `const [data, setData] = useState();` to `const [data, setData] = useState(null);`.

Note that constant re-renders may occur whenever `data` updates. If `data` undergoes frequent changes, exploring alternative strategies like incorporating a loading state into components or conducting data fetching directly within said components could be beneficial.

I encountered an issue where the data I passed to a component ended up being undefined

Answer №1

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